2728215661 has 4 divisors (see below), whose sum is σ = 2729752732. Its totient is φ = 2726678592.

The previous prime is 2728215653. The next prime is 2728215697. The reversal of 2728215661 is 1665128272.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1063086025 + 1665129636 = 32605^2 + 40806^2 .

It is a cyclic number.

It is not a de Polignac number, because 2728215661 - 2³ = 2728215653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2728215631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 765870 + ... + 769423.

It is an arithmetic number, because the mean of its divisors is an integer number (682438183).

Almost surely, 2^2728215661 is an apocalyptic number.

It is an amenable number.

2728215661 is a deficient number, since it is larger than the sum of its proper divisors (1537071).

2728215661 is a wasteful number, since it uses less digits than its factorization.

2728215661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1537070.

The product of its digits is 80640, while the sum is 40.

The square root of 2728215661 is about 52232.3239096252. The cubic root of 2728215661 is about 1397.3104249041.

The spelling of 2728215661 in words is "two billion, seven hundred twenty-eight million, two hundred fifteen thousand, six hundred sixty-one".